This invention relates to a dual flow catheter and more particularly for such a catheter for insertion into a blood vessel to facilitate haemodialysis treatments.
The invention will be described with particular reference to haemodialysis procedures, but it is envisaged that the invention could be put to other medical uses.
The procedure of haemodialysis requires that blood be removed for treatment through a catheter having an intake lumen, and that after treatment, the blood be returned through a return lumen either in a separate catheter or in the same catheter. It has become quite common to provide dual flow catheters which have two lumens arranged one to receive untreated blood and the other to return the treated blood to the patient. Such catheters fall into two distinct types namely "co-axial" catheters and "side-by-side" catheters. The co-axial catheters provide dual flows through a first lumen defined by a central tube and through a second lumen defined by an annular space between the central tube and an outer tube. By contrast the side-by-side catheters provide two similar lumens arranged in parallel one with the other. In both types of catheter one of the lumens is the intake lumen and receives blood from a first location, and the other lumen is the return lumen and returns the blood to a second location spaced downstream in the blood vessel from the first one to thereby minimize the risk of treated blood returning and reducing the efficiency of the dialysis treatment.
Co-axial catheters have some advantages over side-by-side catheters and vice-versa. For instance, in a co-axial catheter openings can be provided around the complete periphery for blood intake to minimize the risk that the catheter will be drawn against a blood vessel thereby occluding the intake openings. By contrast, in a side-by-side relationship, the openings can be provided on one side only and this side can become occluded by engagement with the wall. On the other hand, the side-by-side arrangement tends to have more resistance to kinking when it is bent than does the co-axial catheter.